1. Field of the Invention
The present invention relates to a technique for removing metal contamination deposited on a substrate in a process for fabricating a semiconductor device or the like by using a processing liquid.
2. Description of the Related Art
In recent years, Cu wiring layers have become used instead of Al wiring layers in semiconductor devices fabricating processes to deal with the progressive miniaturization of design rules.
When forming Cu wiring layers in a multilayer structure, a lower Cu wiring layer is formed on a semiconductor wafer, i.e., a substrate, an SiN barrier film and a layer insulating film are formed in that order over the lower Cu wiring layer, a photoresist film is formed over the layer insulating film, the photoresist film is patterned by photolithography to form a resist mask of a desired pattern, and the layer insulating film and the SiN barrier film are etched by dry etching using the resist mask to form contact holes reaching to the lower Cu wiring layer. Then, the resist mask is removed by dry ashing, the residual portions of the resist mask and etch residue remaining in the contact holes, such as fragments of a polymer, are removed by cleaning using a cleaning liquid, such as a hydrofluoric acid solution (HF solution), sulfuric acid solution (H2SO4 solution) or an organic peeling agent, and then a Cu film is deposited over the layer insulating film to form an upper Cu wiring layer on the layer insulating film and to fill up the connecting holes with Cu.
Polymer veils are formed on the side surfaces of the contact holes, respectively, when etching the layer insulating film by dry etching using a plasma produced by ionizing an etching gas. Therefore, the polymer veils remain in the contact holes. When the layer insulating film is etched through such that the lower Cu wiring layer is exposed, Cu is caused to sputter and sputtered Cu particles deposit on the polymer veils. The sputtered Cu particles deposited on the polymer veils must be removed together with the polymer veils.
The semiconductor device fabricating process uses Cu as a plating metal and Cu particles are deposited on the back surface of the semiconductor wafer during plating. Such Cu particles must be removed from the back surface of the semiconductor wafer. The cleaning liquid may be used for removing the Cu particles.
However, the Cu particles cannot be removed by treating the semiconductor wafer simply with the cleaning liquid; first of all, the Cu particles must be oxidized into CuO particles because Cu is insoluble in the cleaning liquid and CuO is soluble in the cleaning liquid.
Although the Cu particles may be oxidized in air, and then the oxidized Cu particles may be removed by a treatment using a chemical liquid, the Cu wiring layer and the plated Cu layer will be dissolved and removed and the Cu layers will be damaged.
It is an object of the present invention to provide a method capable of removing at least two kinds of deposits (e.g., polymer veil and metal contamination) deposited on a substrate without damaging a necessary metal deposit (e.g., metal layer for wiring) formed on the same substrate. More specifically, it is an object of the present invention to provide a substrate processing method and a substrate processing apparatus capable of removing unnecessary metal contamination deposited on a substrate without damaging a necessary metal deposit formed on the same substrate.
According to a first aspect of the present invention, a method of removing a metal contamination deposited on a substrate having a metal layer is provided. The method includes the steps of: creating an inert gas atmosphere around the substrate; supplying oxygen into the inert gas atmosphere to create an atmosphere of the inert gas and oxygen; and supplying a processing liquid onto the substrate disposed in the atmosphere of the inert gas and oxygen; wherein the metal contamination deposited on the substrate is oxidized by the oxygen contained in the atmosphere into metal oxide contamination, and the metal oxide contamination is dissolved and removed with the processing liquid.
The present invention also provides a method of removing a metal contamination deposited on a substrate having a metal layer. The method includes the steps of: creating an inert gas atmosphere around the substrate; supplying a processing liquid onto the substrate disposed in the atmosphere, the processing liquid including an oxygen; wherein the metal contamination deposited on the substrate is oxidized by the oxygen contained in the processing liquid into metal oxide contamination, and the metal oxide contamination is dissolved and removed with the processing liquid.
The present invention also provides a method of removing polymer veil and metal contamination deposited on a substrate having a metal layer with a processing liquid. The method includes the steps of: placing the substrate in a processing space; creating an inert gas atmosphere in the processing space and supplying the processing liquid onto the substrate, thereby dissolving and removing the polymer veil; and creating an atmosphere of the inert gas and oxygen in the processing space and supplying a processing liquid onto the substrate, thereby dissolving and removing the metal contamination oxidized by the oxygen.
The present invention also provides a method of removing a polymer veil remaining on a substrate after forming at least a metal layer on the substrate and an insulating layer over the metal layer and an etching portion of the insulating layer through the insulating layer so as to reach to the metal layer, and a metal contamination included in the polymer veil when the metal layer is sputtered by etching. The method includes the steps of: (a) placing the etched substrate in a processing space; (b) creating an inert gas atmosphere in the processing space and supplying a processing liquid onto the substrate, thereby dissolving and removing the polymer veil to expose the metal contamination, (c) creating an atmosphere containing an inert gas and oxygen in the processing space and supplying the processing liquid onto the substrate after the step (b), thereby dissolving and removing the exposed metal contamination oxidized by the oxygen; and (d) creating an inert gas atmosphere again in the processing space, and supplying the processing liquid onto the substrate after the step (c), thereby dissolving and removing a residual of the polymer veil remaining on the substrate.
The present invention also provides a method of removing a resist mask, a polymer veil and a metal contamination existing on a substrate, the substrate having a metal layer and an insulating layer arranged on the metal layer, the insulating layer being etched while using the resist mask so that the etched portion thereof reaches to the metal layer, the resist mask, the polymer veil and a metal contamination remaining on the substrate after the insulating layer being etched, the metal contamination being included in the polymer veil. The method includes the steps of: (a) placing the etched substrate in a processing space; (b) supplying an inert gas into the processing space to create an inert gas atmosphere in the processing space and supplying a processing liquid onto the substrate, thereby dissolving and removing the resist mask; (c) supplying a processing liquid onto the substrate placed in the processing space of the inert gas atmosphere, thereby dissolving and removing the polymer so that the metal contamination included in the polymer veil is exposed; (d) introducing an oxygen-containing gas into the processing space after the step (b) and (c) to create an atmosphere containing oxygen in the processing space and supplying a processing liquid onto the substrate, thereby dissolving and removing the metal contamination oxidized by the oxygen; and(e) stopping introducing the oxygen-containing gas to create an inert gas atmosphere again in the processing space and supplying a processing liquid onto the substrate after the step (d), thereby dissolving and removing a residual of the polymer veil.
The present invention also provides a method of removing at least two kinds of deposits deposited on a substrate, said method comprising the steps of: placing the substrate in a processing space; creating a first atmosphere of a first oxygen concentration in the processing space; dissolving and removing a first kind of deposit of at least the two kinds of deposits by supplying the processing liquid onto the substrate in the processing space of the first atmosphere; creating a second atmosphere of a second oxygen concentration different from the first oxygen concentration in the processing space; and dissolving and removing a second kind of deposit of at least the two kinds of deposits by supplying a processing liquid onto the substrate in the processing space of the second atmosphere.
According to the second aspect of the present invention, a substrate processing apparatus that removes metal contamination deposited on a substrate provided with a metal layer is provided. The apparatus includes: a processing vessel defining a processing space in which the substrate is placed; a first gas supply pipe for supplying an inert gas into the processing space; an second gas supplying pipe for supplying a gas including oxygen gas into the processing space; a gas discharging pipe for discharging an atmosphere in the processing space; a processing liquid supplying pipe for supplying a processing liquid into the processing space, the processing liquid being capable of removing the metal contamination deposited on the substrate; and a draining pipe for draining the processing liquid used in the processing space.